The petroleum industry is increasingly turning to heavy crudes, resids, coals and tar sands as sources for feedstocks. Feedstocks derived from these heavy materials contain more sulfur and nitrogen than feedstocks derived from more conventional crude oils, requiring a considerable amount of upgrading in order to obtain usable products therefrom.
Bulk (unsupported) catalysts have recently been disclosed for use in the hydroconversion of heavy crudes. US Patent Publication No. 20070161505 discloses an ultra-dispersed catalyst composition having a median particle diameter between 30-6000 nm. US Patent Publication No. US2009023965 discloses a catalyst composition with an emulsion of an aqueous phase in an oil phase and wherein the aqueous phase comprises an aqueous solution containing a group 6 metal and a group 8, 9 or 10 metal. US Patent Publication No. US2005241993 discloses the upgrading of heavy oil using individual metal sulfide catalyst molecules and/or extremely small particles that are colloidal in size (i.e., less than 100 nm and preferably less than about 1 nm).
In the hydroconversion processes of the prior art as disclosed in US Patent Publication No. US2005241993, after the initial slurry phase reactor, the upgraded feedstock containing residual or molecular catalyst is further processed in another reactor in series, e.g., an ebullated bed reactor with the residual colloidal or molecule catalyst providing additional catalytic hydrogenation activity. The hydroconversion is carried out in a pilot plant at operating pressure ranging from 1500 to 2100 psi, and at a hydrocracking temperature ranging from 410° C. (770° F.) to 460° C. (860° F.). Underhigh pressure, high temperature hydrocracking conditions, solid deposits tend to form, plugging up equipment and cutting down operation time.
There is still a need for improved processes to upgrade heavy oil, particularly a heavy oil upgrade process that can operate at a lower pressure than specified in the prior art and/or with less solid build-up in the reactor system. There is also a need to slow down the deactivation of bulk catalysts for use in the upgrade of heavy oil.